1. Field of the Invention
The present invention relates to an electrostatic latent image developing apparatus for use in the electrophotographic process or the like for developing electrostatic latent images formed on an image bearing surface.
2. Description of the Prior Art
Such electrostatic latent image developing apparatus heretofore provided are generally so adapted that a developer retained on the outer peripheral surface around a developing sleeve is transported circumferentially of the sleeve to a developing station where the sleeve is opposed to an image bearing surface to develop an electrostatic latent image formed on the image bearing surface. With copying machines made more compact in recent years for installation in smaller spaces, it is also highly desired to compact the developing apparatus itself.
After the developer has passed through the developing station and been used for development in the developing apparatus, the developer has a reduced toner concentration and therefore needs to be removed from the outer periphery of the developing sleeve for replacement by a fresh portion of developer supplied to the sleeve surface.
For this purpose, the used developer is usually scraped off the sleeve surface by a scraper disposed downstream from the developing station and held in pressing contact with the sleeve surface as disclosed in U.S. Pat. No. 4,392,735.
However, this requires a space for providing the scraper, entailing the problem of making the developing apparatus larger and costly to fabricate. When the developing sleeve is made rotatable for transporting the developer, improved transportability can be achieved effectively by forming minute indentations in the outer peripheral surface of the sleeve as by sandblasting. Nevertheless, if the scraper is provided in pressing contact with the surface of such a developing sleeve, there arises the problem that the toner lodges in the minute indentations owing to the pressing contact to cause a filming phenomenon.
On the other hand, the fresh developer portion supplied to the sleeve surface is further transported in an amount controlled by a bristle height restricting plate at a position upstream from the developing station. Consequently, another problem is encountered. The developer restrained by the restricting plate and retained at the upstream side of the plate is subjected to a stress by being pressed against the restricting plate by portions of developer which are subsequently transported forward in succession. This promotes deterioration of the developer resulting in a shortened life.